The Section focuses its research on the functions of the human prefrontal cortex and cognitive neuroplasticity. We continue to refine a model developed in the Section that specifies some of the characteristics of the prefrontal cortex's underlying cognitive architecture and representational knowledge. We have determined that ease of access to knowledge stored in the prefrontal cortex is determined by the category and familiarity of that knowledge. In addition, failure to selectively retrieve such knowledge leads to impaired plan development and/or execution. Activating knowledge stored in prefrontal cortex allows for control processes to manage information that has to be kept temporarily active. The control processes in the prefrontal cortex appear to be forms of social and non-social knowledge uniquely stored in the prefrontal cortex. Such knowledge helps modulate more primitive behaviors such as aggression. Other research in the Section shows that the amygdala plays an important role in scaling the emotional content of stimuli. In an effort to better understand some aspects of cognitive neuroplasticity, we have examined the learning rate of patients recovering from brain damage and with deficits on the task of interest and compared their performance to matched controls. There is some indication that patients can show new learning in deficit areas but it is not clear that if new learning is without a cost to preserved cognitive functions. Our current work is analyzing whether transcranial magnetic stimulation can enhance retrieval of information from memory and facilitate recovery of function from brain damage. The section also utilizes positron emission tomography (PET), functional magnetic resonance imaging (fMRI), and transcranial magnetic stimulation (rTMS) to map planning processes, representational knowledge, reasoning processes, social cognition, reward systems, number processing and calculation to brain. For example, over the last year, we have determined with fMRI the importance of the anterior prefrontal cortex for multitasking, task-switching, and adaptive behavior. We have used rTMS to facilitate the speed of analogical reasoning in healthy normal control subjects possibly providing a framework to use rTMS to aid rehabilitation of brain-injured patients. The Section utilizes data from normal control studies, patient studies, functional neuroimaging, and rTMS to provide convergent evidence about the functions of the human prefrontal cortex and cognitive neuroplasticity.